The results indicate that BRWN is associated with increased phosphorus acquisition and that this trait may have value for selection of genotypes with better performance in low phosphorus soils.

Sclerotinia sclerotiorum, causal agent of white mould, is the most destructive and widely distributed soilborne pathogen of common bean during the autumn–winter season in Brazil. Nevertheless, little is known about the genetic structure of the pathogen population. Microsatellite (SSR) markers and mycelial compatibility groups (MCGs) were used to characterize 118 isolates collected from 20 bean fields located in the most important growing regions of Minas Gerais State (MG). Additionally, the genetic variability among 10 isolates obtained from a single sclerotium was investigated in 10 different sclerotia. Seventy SSR haplotypes and 14 MCGs were identified among the 118 isolates. The genetic differences within bean growing areas accounted for most of the genetic variation (72%). Despite the relatively high genotypic diversity, the SSR loci were at linkage disequilibrium. Moreover, 70% of the isolates were assigned to only two MCGs, and haplotypes of a given MCG were closely related. The discriminant analysis of principal components revealed five groups. There was strong genetic differentiation between isolates collected in one municipality in southern MG when compared to other regions. Common bean resistance to white mould should be assessed with representative isolates of the five genetic groups and, if possible, of the different MCGs detected in the present study. One to five haplotypes were detected among the 10 isolates obtained from a single sclerotium. Therefore, in order to ensure genetic identity of an isolate, hyphal tip or monoascosporic isolates should be used.

Mungbean cultivation in summer in Viçosa and Prudente de Morais, Minas Gerais State, BrazilWe evaluated 25 genotypes of mungbean in the summer in Viçosa (sown in December 1997) and Prudente de Morais (sown in January 1999): nineteen lines from the Asian Vegetable Research Development Center, four from the Instituto Nacional de Pesquisa da Amazônia, one cv. from Peru besides cv. Ouro Verde. Yield varied from 1.2 to 2.0 t/ha in Viçosa, and from 1.3 to 2.6 t/ha in Prudente de Morais. Several lines yielded more than the cultivar Ouro Verde, standing out the line VC 3984-B-2-B-4-1-B due to the resistance to prostration. Mungbeans were well adapted in the summer season providing high yield in relatively short time.

No abstract

White mold of common bean (Phaseolus vulgaris), caused by Sclerotinia sclerotiorum, is a major yield-limiting disease during the fall-winter season in Brazil. This study was conducted to evaluate the efficacy of decreasing within-row densities for an indeterminate growth habit (type IIIa) cultivar, keeping constant the between-row spacing of 0.5 m, to manage the disease. A modification of within-row plant distributions was also attempted in order to reduce white mold intensity. The study was conducted with sprinkler irrigation in two growing seasons (2000 and 2001) in Viçosa, State of Minas Gerais, Brazil, in an area naturally infested with sclerotia. In 2000, treatments were arranged as 3 × 2 × 2 factorial combination of within-row densities (15, 7.5, or 5 plants/m), within-row plant distributions (single and equidistant plants or equidistant groups of three plants), and fluazinam treatments (with or without). In 2001, 16, 12, 8, or 4 plants/m were combined with fluazinam treatments. Fluazinam was applied at both flowering onset and 10 or 13 days later. Average incidence was 92.6% in 2000 and 77.8% in 2001; severity index was 69.8% in 2000 and 40.2% in 2001; and yield was 1,656 kg/ha in 2000 and 2,542 kg/ha in 2001. White mold decreased and yield increased as within-row densities were reduced, regardless of fluazinam treatments. A distribution of equidistant groups of three plants was ineffective in reducing disease. The use of 4 equidistant plants/m in infested irrigated areas was an effective strategy in white mold management.

Molybdenum (Mo) reserve in large seeds can complement Mo uptake by plants from soil, but the content of Mo in common bean (Phaseolus vulgaris L.) seed for this purpose is unknown. We hypothesized that 3.639 ± 0.751 μg Mo seed -1 would be suffi cient to complement Mo uptake by irrigated common bean plants from a Mo-poor soil. Th ree fi eld experiments were performed in a clayey Ultisol naturally infested by native strains of Rhizobium in Zona da Mata, Minas Gerais, Brazil. Treatments were arranged as 4 × 2 factorial combination of Mo contents in seeds [small (0.007 ± 0.007 or 0.248 ± 0.057 μg Mo seed -1 ) or large (3.639 ± 0.751 or 6.961 ± 1.844 μg Mo seed -1 )] and Mo spraying treatments (90 g ha -1 or unsprayed) with six replications. Phosphorus, N (25 kg ha -1 ), and K were applied together in the furrow during planting time. No topdressing N was applied. Final plant population and seed yield were evaluated in two experiments. Molybdenum contents in the seeds did not aff ect plant population. On average, unsprayed plants from seeds with small Mo contents yielded 1785 kg ha -1 , while those from seeds with large Mo content yielded 2109 kg ha -1 . Foliar application of Mo increased plant N status, plant growth, and yield in plants originated from seeds with small Mo content, but not in plants grown from seeds with large Mo content. We conclude that 3.639 ± 0.751 μg Mo seed -1 suffi ciently complement the Mo uptake by common bean plants from soil.

ABSTRACT. We evaluated the effects of split molybdenum (Mo) application at the reproductive stage of the common bean on seed Mo content (SMoC) and seed quality in two trials in the Zona da Mata region, Minas Gerais. Plants were sprayed with 100 or 600 g Mo ha -1 at the V4 stage. The higher dose was also split into 100(V4)+500(R5), 100(V4)+500(R7), 100(V4)+250(R5)+250(R7), and 100(V4)+150(R5)+350(R7). SMoC from plants sprayed with 600 g (five treatments) was 3.7-or 62-fold higher than those sprayed with 100 g, with seeds from the former treatments exhibiting slightly poorer quality. Application of 100 g at V4 + 500 g at the reproductive stage (four treatments) increased SMoC 1.6-or 2.7-fold compared with SMoC from plants sprayed with 600 g at V4. Split application of 500 g with two sprays increased SMoC by 11% (p = 0.257) or 16% (p = 0.013) compared with one spray of 500 g. SMoC can be higher with Mo applied at R7 (pod formation) instead of at R5 (pre-flowering), without impairing seed quality. Thus, split Mo application between the R5 and R7 stages of the common bean saves molybdic fertilizer to produce Morich seeds, with only a slight decrease in seed quality.Keywords: Phaseolus vulgaris, seed molybdenum, seed quality, seed vigor, seed germination.Parcelamento da aplicação do adubo molíbdico na fase reprodutiva do feijão-comum aumenta o conteúdo de molibdênio na semente RESUMO. Avaliamos os efeitos de parcelamentos da aplicação de molibdênio (Mo) na fase reprodutiva do feijão-comum no conteúdo de Mo na semente (CMoS) e na sua qualidade fisiológica em dois ensaios na Zona da Mata, Minas Gerais. Pulverizaram-se feijoeiros com 100 ou 600 g Mo ha -1 na fase V4. Esta última dose também foi parcelada: 100(V4)+500(R5), 100(V4)+500(R7), 100(V4)+250(R5)+250(R7) e 100(V4)+150(R5)+350(R7). O CMoS de plantas pulverizadas com 600 g (cinco tratamentos) foi 3,7 ou 62 vezes maior que o das pulverizadas com 100 g; sementes deste tratamento apresentaram qualidade ligeiramente melhor que as daqueles. Aplicação de 100 g em V4 + 500 g na fase reprodutiva (quatro tratamentos) aumentou 1,6 ou 2,7 vezes o CMoS comparativamente ao CMoS de plantas adubadas com 600 g em V4. Parcelamento de 500 g em duas pulverizações aumentou em 11% (p = 0,257) ou 16% (p = 0,013) o CMoS comparativamente a uma pulverização. O CMoS pode ser mais alto quando se pulveriza o Mo em R7 (formação de vagens) comparativamente a R5 (pré-floração), sem prejuízo à qualidade da semente. Logo, o parcelamento do Mo nessas duas fases do feijão-comum economiza fertilizante molíbdico para produzir sementes ricas em Mo, com ligeira redução da qualidade da semente. Palavras-chave:Phaseolus vulgaris, molibdênio na semente, qualidade da semente, vigor da semente, germinação da semente.

A escolha e o uso adequado de bicos de pulverização são essenciais para a correta aplicação de agrotóxicos. Este trabalho teve como objetivo avaliar o espectro de gotas de bicos de pulverização hidráulicos de jato plano padrão e de jato cônico vazio, com diferentes vazões nominais. Em ambiente controlado, avaliou-se o espectro de gotas por meio de um analisador a laser de gotas em tempo real, nas faixas de pressão de 200 a 400 kPa para os bicos de jato plano, e de 400 a 600 kPa para os bicos de jato cônico vazio. Realizou-se também um estudo teórico sobre a distância horizontal percorrida por gotas de tamanho conhecido. Os bicos de jato cônico vazio apresentaram gotas de menor tamanho em relação aos de jato plano e, por isso, proporcionaram maior densidade de gotas depositadas sobre a superfície-alvo. Todos os bicos apresentaram densidade de gotas superior a 110 gotas cm-2. No entanto, o potencial de deriva foi alto, principalmente o dos bicos de jato cônico, requerendo estratégias para sua redução. É possível estimar a distância horizontal percorrida por gotas de tamanho conhecido.